In electrophotographic reproduction devices, for example a printer, a host computer sends and receives control data to command various operations from the host computer to the printer. One type of control data relates to the positioning of page data to be generated on a print surface.
Typically, in printer systems, a printed image is formed using digital data that resides in the page memory of a processor. In one type of printer system, the image from the page memory is formed on a print surface using a scanning laser beam. An area of the print surface on which the image is formed is referred to as a picture element (PEL). One scan of the laser beam across the print surface forms a row of PELs, referred to as a scan row. The image from the page memory is formed with multiple scan rows.
The first PEL must be properly positioned in order for the scan rows to be horizontally and vertically aligned on the print surface. Defects in the data path between the host computer and the printer, however, may cause the scan rows to "walk" or be misaligned. This misalignment may go undetected if the user of the printer system does not inspect each printed page. In addition, testing individual components within the data path for defects adds to manufacturing cycle time and, thus, increases the cost of the printer systems.